Improvement in process for making concave circular saws



ibtiir mes @anni effin,

THOMAS s. DIssToN, or PHILADELPHIA, PENNSYLVANIA, AssIGNoR To HIMSELFAND HENRY DISSTON' & SON, OF SAMEILACE.`

Letters Patent No. 109,881,.`da,ted December 6, 1870.

IMPROVEMENT-'IN PROCE-SS FOR-MAKING CIONCAVE CIRCULAR SAWS.

'The vSchedule referred to In these Letter-i Patent and making part ofthe lame.

I", THOMAS S. DISSTON, of Philadelphia, county of Philadelphia, State ofPennsylvania, have'invented a .Mode of Manufacturing Ooncavo-convexOircular-Saw Blades, f which the following is a specification.

Nature and Object of Ihre Invention.

My invention consists of a mode or process, fully described hereafter,of manufacturing concave-convex circular-sawblades, the saidprocess'being much more economical than the plan of hai-nmering theblades to.A

the desired shape, as heretofore practiced, and theblades themselvesbeing more uniibrmlyltrue thanordinary blades of this class.

Description of tbe Accbmpan ying Drawing. -Figure 1 is a face view ot'the saw-blade, and Figure 2 a diagramillustrating myprocess.

General Description. In making concave-convex saws, which areextensively used in the manufacture of barrels, &c., it has beenl thepractice to reduce a dat blade to the desired shape by hammering it-amost tedious and experihowever, the latter should be heated to such ade? gree that, when brought into contact with the blade, they cannotchill the surface of the same.

The desired shape having been '.imparted to the blade, vthe next part ofthe process' is that of hardl ening, which may be accomplished in theusual man- I ner,' that is, by immersing the blade while it is Aat theproper heatin water, oil, or other liquid.-

Atterthis the blade has to be subjected tothe last process, that is,tempering or depriving the steel of its brittle character, by reheatingto a given temperature. This I effect by dies similarlto thoseused inthe llst instance for imparting theconcavoconvex shapeto the blade,thedies being properly heated so asV to impart the desired temper.

In the preliminary hardening ofthe blade the latter is apt to lbecomemore or less distorted, but the distortions are removed by tempering theblade between dies of the shape which th-blade has to, assume; iii

fact, a concave-convex saw-blade manufactured according to my process isnot only cheaper, but more uniformly true throughout, than such as aremade by the hammering process.,l Y

I do not desire to claim separately any of the op- Yerationswhich-constitute my process; but

I claiin- I The process rif-manufacturing concave circniar saws by thewhole series ot'opcrations described and in the following order,'namely,cutting the teeth and central opening in a circular plate of steel,heating'said plat-c, compressing the same between' heated dies,hardening it, and theutempcring between heated dies, as set forth. l y fIn testimony whereof, I have signed my name to this specification in thepresence of two subscribing Witnesses. I THOMAS S. DISSTON.

Witnesses:

A. H. SHOEMAKER, H. HowsoN.

